In this longitudinal investigation, the relationship between IQ scores at age four and a variety of factors related to pregnancy, delivery, postnatal status and social environment was examined in a large biracial sample of children enrolled in the Collaborative Study. The effects of predictors found to be significantly correlated with IQ were investigated first individually. Then the combined effects of these variables on IQ and their combined ability to discriminate between low and normal IQ groups were examined. Bibliographic references: Broman, S.H., Nichols, P.L., and oennedy, W.A.,: Preschool IQ: Prenatal and Early Developmental Correlates. Hillsdale, N.J.: Lawrence Erlbaum Associates (distributed by Halsted Press of John Wiley & Sons) 1975, 360 pp.